Crystal holder for x-ray monochromators



March 24, 1964 w. GesT-z ETAL 3,126,478

CRYSTAL HOLDER FOR X-RAY MONOCHROMATORS Filed Feb. 20, 1961 27 74 79 24 Fig. 7

lnvengzgors WW1 WWW United States Patent F 3,126,478 CRYSTAL HOLDER FOR X-RAY MONO- CHROMATORS Wolfgang Gtitz and Helmut Giinther, Jena, Germany, assignors to VEB Carl Zeiss Jena, Jena, Germany Filed Feb. 20, 1961, Ser. No. 90,579 4 Claims. (Cl. '2'50-51) This invention relates to a crystal holder for X-ray monochromators.

In X-ray spectroscopy use is frequently made of bent crystals for forming in the regular way an image of the entrance slit or the focus of the X-ray tube on the receiver. As compared to plane crystals, bent crystals help considerably towards increasing the luminosity and definition of the spectral lines, but it is rather difficult to bend and mount the crystals or crystal plates, which are comparatively thin and thus prone to suffer deformations grossly impairing the results of measurements.

Bending and holding devices are known in which steel springs press the crystal plate on either of its longitudinal margins against a curved bearing surface. Devices of this kind are however rather complicated in both construction and manipulation. To compensate for the partial pressures of the springs on the crystal plate it is necessary to associate with each spring a screw that can be rotated to minimize the stress in the crystal, which is recognizable for instance by the shape and the acuity of the focal lines. To remove as much as possible of those pressures on the crystal plate, a known holding device (Zeitschrift fiir Physik, vol. '82, 1933, pages 501 to 528) contains between the springs and this plate a number of pressure-compensating plates which, while improving the mode of operation, do nothing to benefit the construction of the holding device and to facilitate its manipu lation.

Another bending and holding device (German Patent 963,198) is a block of plastic material which guarantees uniform pressure in that its pressure-receiving surface is the negative replica of the adjacent bearing surface, the single loads on the crystal plate being thus replaced by an area load. However, this area load acts also on that part of the crystal plate which the bearing surfaces leave un supported for free-X-ray incidence. Inherently the plastic material will permit the area load to create a bending effect above the said unsupported part of the thin crystal plate and cause the ends of the focal lines to disperse considerably, which is particularly disadvantageous if a plurality of materials are to be examined for instance as to purity at the same time and in one measuring process.

The crystal deformations due to the pressure means are all avoided by the method of free bending (Zeitschrift fiir Naturforschung, vol. 13a, 1958, pages 356 and 357) if the crystal plate is supported only at two opposite margins and the respecting supports are rotated relatively to each other or so displaced that the line of curvature of the crystal plate is always circular. Such supporting of the crystal plate is effective only if this plate has the same cross-section everywhere. Moreover, it is subject to the unfavourable influence which the transverse curvature in consequence of the elasticity constant of the crystal plate exerts on the image of the focal line.

The crystal holder according to the invention has a plurality of strips extending in the direction of the curvature of the bearing surface, the ends of said strips being connected to the body of the bearing surface. The one ends of said strips can be fast with the said body and the other ends of said strips can be detachably connected to the said body.

According to a further feature of the invention maximum adjustment of the X-ray illumination of the crystal surface is obtained by the use of two strips which in- 3,126,478 Patented Mar. 24, 1964 'fiuence only those parts of the crystal plate which lie on the bearing surface. To ensure reliable bend and hold of the crystal plate while preventing any damage to its margins, the strips are conveniently provided on the margins of the bent crystal plate in such a manner as to be approximately tangential to the surface of said plate. The strips can be connected to each other at their detachable ends and can be made to act on the crystals by means of one single device which is similar to the beam of a balance. Moreover, this device makes it possible to compensate for potential small differences in the bending forces that act on the two halves of the crsytal plate.

The accompanying drawing illustrates schematically and by way of example one embodiment of the invention, FIGURES 1, 2 and 3 representing a cross-section, an elevation and a side-elevation, respectively.

The legs 11 and 12 of a body 13 of U-shaped crosssection have at their free ends bearing surfaces 14 and 15, respectively, both of which are parts of one and the same cylindrical surface. These bearing surfaces 14 and 15 are the supports of an asymmetrically cut crystal plate 16 the position of which is exactly defined by a mount 17. The space 18 intervening between the legs 11 and 12 of the body 13 is for unobstructed X-ray passage. The crystal plate 16 is bent and held in position by two steel strips 19 and 20. The one ends of these strips 19 and 20 are clamped by means of reenforcing plates 21 and 22, respectively, and screws 23 to the body 13. The other ends of the strips 19 and 20 are connected by means of reenforcing plates 24 and 25, respectively, and screws 26 to a rod 27. This rod 27 is rotatable about a pinion 29 fast with a rod 28 parallel to the cylinder generatrix. The rod 28 connects the legs of a scale balance 30 which corresponds to the U-shape of the body 13 and Whose legs have recesses 31 and 32, respectively, for holding the scale balance 30 on knife edges 33, 34 fast with the body 13 and constituting the axis of tilt of said balance. The part connecting the legs of the scale balance 30 has an attachment 35 which can be influenced by a screw 36 extending into the body 13.

Tilting the lower part of the scale balance 30 to the body 13 strains the steel strips 19, 20. The crystal plate 16 which is placed on the bearing surfaces 14, 15 and whose one edge touches the mount 17 is accordingly so bent and held in position that its entire length lies against the bearing surfaces. In this position, the scale balance 30 is held by the screw 36. Loosening this screw 36 causes the strips 19, 20 to relax, so that the crystal plate 16 can be removed or exchanged for another.

We claim:

1. Crystal-plate holder for X-ray monochromators, comprising a body of U-shaped cross-section, each of the two legs of said body having at its free end a curved hearing surface for the crystal plate, and two strips lying in the direction of the greatest dimension of said two hearing surfaces, said crystal plate being supported between said legs and said strips, the ends of said strips being all connected to said body, and the breadth of said strips being such that they act only on the parts of the crystal plate which come to lie on the bearing surfaces.

2. Crystal-plate holder for X-ray monochromators, comprising a body of U-shaped cross-section, each of the two legs of said body having at its free end a curved hearing surface for the crystal plate, and two strips lying in the direction of the greatest dimension of said two hearing surfaces, said crystal plate being supported between said legs and said strips, the one ends of said strips being detachably connected to said body and the other ends of said strips being undetachably connected to said body, the detachable connections being on the one side of said body and the undetachable connections being on the other side of said body, and the breadth of said strips being such that they act only on the parts of the crystal plate which come to lie on the bearing surfaces.

3. Crystal-plate holder for X-ray monochromators, comprising a body of U-shaped cross-section, each of the two legs of said body having at its free end a curved bearing surface for the crystal plate, and two strips lying in the direction of the greatest dimension of said two bearing surfaces, said crystal plate being supported between said legs and said strips, the ends of said strips being all connected to said body, said strips when taut being approximately tangential to the crystal surface at their connections with the crystal plate margins facing the body, and the breadth of said strips being such that they act only on the parts of the crystal plate which come to lie on the bearing surfaces.

4. Crystal-plate holder for X-ray monochromators, comprising a body of U-shaped cross-section, each of the two legs of said body having at its free end a curved bearing surface for the crystal plate, and two strips lying in the direction of the greatest dimension of said two bearing surfaces, said crystal plate being supported between said legs and said strips, the one ends of said strips being detachably connected to said body and the other ends of said strips being undetachably connected to said body, the detachable connections being on the one side of said body and the undetachable connections being on the other side of said body, means connecting the detachable ends of said strips to each other and to said body, the breadth of said strips being such that they act only on the part of the crystal plate which come to lie on the bearing surfaces.

References Cited in the file of this patent FOREIGN PATENTS 

1. CRYSTAL-PLATE HOLDER FOR X-RAY MONOCHROMATORS, COMPRISING A BODY OF U-SHAPED CROSS-SECTION, EACH OF THE TWO LEGS OF SAID BODY HAVING AT ITS FREE END A CURVED BEARING SURFACE FOR THE CRYSTAL PLATE, AND TWO STRIPS LYING IN THE DIRECTION OF THE GREATEST DIMENSION OF SAID TWO BEARING SURFACES, SAID CRYSTAL PLATE BEING SUPPORTED BETWEEN 